1. Field
Embodiments relate to an optical element using a multicore optical fiber grating and a method for processing an optical signal using the same.
2. Description of the Related Art
A multicore optical fiber is an optical fiber including several cores and a cladding surround the cores. The multicore optical fiber may be widely used in various fields including, for example, a passive element for implementing an optical communication network, an optical sensor, an optical spatial division multiplexer, a wavelength multiplexer or a wavelength demultiplexer of an optical communication system, or the like.
FIG. 1 is a schematic view showing a conventional multicore optical fiber. Referring to FIG. 1, the multicore optical fiber may include an input end 11 and an output end 12 while extending in one direction. Regarding the input end 11, the multicore optical fiber may include an inner core 111 located at or near the center of an optical fiber, and at least one peripheral core 112 arranged around the inner core 111. An inner core 121 and at least one peripheral core 122 depicted at the output end 12 respectively correspond to the inner core 111 and at least one peripheral core 112 of the input end 11. For example, the inner core 111 at the input end 11 and the inner core 121 at the output end 21 may designate sections of a single core in different directions.
As shown in FIG. 1, in the conventional multicore optical fiber, the diameter of the inner core 111, 121 is identical to the diameter of the peripheral core 112, 122. In addition, the refractive index of the inner core 111, 121 is also identical to the refractive index of the peripheral core 112, 122. Therefore, if cores sufficiently approach each other in the multicore optical fiber, optical coupling between propagation modes may occur among the cores at substantially all wavelengths. In other words, optical signals of all wavelength bands, incident to the inner core 111, may be coupled with neighboring peripheral cores 112. As a result, an incident light 1 incident to the inner core 111 at the input end 11 is coupled with neighboring cores in the multicore optical fiber and outputs in a form of an output light 2 at the output end 11 through the inner core 121 and at least one peripheral core 122.
Therefore, if an optical element is implemented using a conventional multicore optical fiber configured described above, it is difficult to make an optical element which allows a specific wavelength channel to be dropped or added. An add-drop filter based on a Mach-Zehnder interferometer may be used to drop or add a wavelength channel, which however has problems such as low stability, large product volume and difficult fabrication.